Refilling laptop batteries!

Case with cells removed
This is a picture of the battery case and charging electronics after I unsoldered the original li-ion cells.  

Two li-ion cells ready to be soldered A pack of two li-ion cells soldered and ready to be used
Here I have two Li-Ion cells ready to solder together into a parallel pack. The technique that I found to work  best was to insert a coil of small electronic solder between the tab and the bottom of the next battery, making sure that the solder never overlapped, so that their was always only one thickness of solder thick at any particular place. Then, I'd hold down the end of the tab with a screwdriver (to make sure it didn't bounce back up while the solder was still hot) and heat the tab with heavy downward pressure from a heavy duity (stained glass) soldering iron for a few seconds. I'd press down until the solder visiblely melted (usually accompanied by a puff of resin smoke) and the tab settled down. Then I'd remove the iron while keeping pressure with the screwdriver.

Important safety note: At the factory, tabs are welded to li-ion cells very quickly. Li-Ion cells will catch fire explosively if they are overheated. It is very important that you do not leave a soldering iron on the cells long enough to raise their internal temperatures to dangerous levels. Heat the tab, melt the solder, and then remove the iron. 

You will note that I used one set of tabs to attach the two cells, and the other set of tabs was positioned 90 degrees off axis, to be used  to connect to other packs of cells. Note that I'd use tape to hold the cells closely together while soldering them, but would remove the tape later to make them fit into the battery holder.

One pack attached to charging electronics

Here is my first pack, soldered to the charging electronics. Note that I have temporarily covered the exposed positive ends of these cells with clear plastic tape. This tape insulation is very important! It keeps this pack of cells from accidentally shorting through the pack of cells that I will add next. The process involves laying the cells on top of each other while soldering, and it is very dangerous to short out li-ion cells. (All of the charging electronics and fuses in the battery are designed just to keep that from happening.) Note that other things on your workbench can short out li-ion cells. For example, a coil of solder conducts electricity very well, at least until it melts. So do screwdrivers and pliers, and they are less likely to melt. Li-Ion cells are usually stored and shipped 40% full to prolong their life, and the ones I had certainly did spark a few times. A small spark here or there won't hurt anything, but if you short a cell for longer than a moment, it will begin to overheat and you could get into a runaway situation where it eventually catches fire explosively. Don't do that!

Once I've safely insulated the ends of these cells, I add the 2nd pack and solder them together.

Two packs on top of each other termporarily for soldering

After the tabs are soldered together, you can unfold the 2nd pack and lay it down flat.

Two packs, after unfolding

When soldering existing metal tabs from the charging electronics to the cells, I found it best to coat the tabs with solder first, and then attach them to the cells. Below you can see a pre-existing tab that I pre-soldered before attempting to attach it to the back of the cells.

Pre-Soldered tab, ready to be attached to the base of a cell

Note that the first and second pack have a good space between them (by design) in the battery holder, which leaves plenty of room for the solder tabs to be folded between the two packs of cells. However, the second and third packs must be mounted much closer together. Because I did not have a custom manufactured set of solder tabs, I found it easier to just butt the batteries up against each other and join the solder tabs above the cells.

All 3 packs in place

Now, I have all three packs connected in serial, and to the charging electronics. All that remains is to find some very sticky double-sided tape to affix everything to the interior of the battery case. I suggest you use carpet-tape (designed for tacking down carpet), which appears to be about as strong as the original tape I removed from the case when disassembling it.

Carpet tape on top of cells Battery case re-assembled

Once the tape is in place, all that remains is to snap the two halves of the battery case together, being careful to get all of the tabs in the right slots. Everything snaps together with a satisfying "clicking" noise, and the battery is as good as new. If you do not remove the manufacturers sticker (as I did) and are careful to use a plastic tool and not leave scrape marks when prying the battery apart  (as, once again, I did) the battery will look practically like new.

But how does our existing charging charging circuitry deal with the brand new li-ion cells? 

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#1 MAKE: Blog on 03.01.07 at 2:42 pm

HOW TO – Refilling laptop batteries…

Jay writes – Here’s a step by step tutorial on how to “refill” laptop batteries by replacing the Li-Ion cells. By purchasing higher capacity cells than your laptop uses normally, you can super-charge your battery life! Jay’s Technical Talk……

#2 Erik Robinson on 03.01.07 at 10:13 pm

Jay, thanks so much for the Info! I had never even thought of that!
I bought an old panasonic toughbook for my daughter from ebay, and of course, the battery was dead. cost of a replacment on ebay: about a hundred bucks. a quick google search for the cells found them at about 3.50 each. total cost for 9 cells plus shipping:$45.26
you just saved me at least 50 bucks!
Thanks again! -

#3 Ajury on 03.02.07 at 10:30 am

Great stuff!

Thanks for mentioning explosive batteries. They really stink too.

Its pretty easy to injure the batteries even if you dont explode them with the soldering iron. (= less capacity)

#4 Gizmodo on 03.02.07 at 12:48 pm

DIY: Refill Your Own Laptop Batteries…

Everyone knows that after a substantial amount of use, laptop batteries are destined for failure, but hold your horses before clicking the “Buy” link on a new $100-plus laptop battery. Jay picked up some OEM lithium-ion batteries and decided to……

#5 Tundra Wookie on 03.02.07 at 2:59 pm

Warning, from the voice of experience: in addition to taking care to not overheat cells while soldering, also take care to not physically damage or deform the cells such as dent, ding or put undue pressure on them when re-assembling. Any physical damage can lead to an internal short and if the battery has sufficient charge, it will overheat and leak, smoke and/or explode, in that sequence.

#6 chia on 03.02.07 at 6:50 pm

BEWARE !!! , not all notebook battery can be refill like this way , some new smart notebook battery got a flash chip inside , when u took off the battery the chip is automatic erase , so you never can recharge your battery , even you change the new cell inside, u only can refill some old nb battery like 5 or 6 year old notebook !

#7 christooss on 03.04.07 at 10:46 am

How to know if flash chip is present on battery?

BTW Very nice howto

#8 Daren on 03.09.07 at 6:07 am

Plesae could someone tell me where I can purchase these batteries from!?!? The ones that go inside the battery pack.

#9 Jay on 03.09.07 at 8:46 am

I bought the batteries (li-ion cells) from (it’s listed on the first page of the post.) Others sell them too, if you do a search for “18650 li-ion” on plenty of dealers come up.

#10 Gizmodo Japan(ギズモード・ジャパン) on 03.11.07 at 12:18 am


  ラップトップのバッテリーって遅かれ早かれ寿命がくるものです。 新品は100……

#11 MDAWOOD on 03.13.07 at 1:16 pm

I got IBM R32 LAPTOP please advise how to open the battery pack and replace with an OEM cells..? Do you have some pics
Much appreciated. Best regards

#12 Jay on 03.13.07 at 9:01 pm

The R batteries should be very similar to the X batteries. I used a Cell Phone opening tool (Green plastic pry bar) to gradually crack open the battery at the seam and “un-snap” each of the clip in snaps that hold the two halfs together.

#13 Phil C. on 03.17.07 at 4:04 pm

I followed your lead and rebuilt my A20m’s battery pack (original IBM # 02K6618). I bought my cells from batteryspace and got the 2600 mAh cells. Worked great! Now, about resetting that flash chip…my pack has an AS358D flash chip. I’ve spent a lot of time looking on the web for info on reflashing the chip, and have only found one thing: “Smart Battery Workshop,” a program that claims it can read and reflash the chip. Problem: another company bought the program’s creators, and now only rebuilds batteries for you. The program was apparently well copy-protected and I can’t find a hacked copy. If anyone can find a way to reset the flash chip, we’ll all be good-to-go.

#14 Student Journalist on 04.11.07 at 4:44 pm

For those of you not as technicly inclined as most on this forum, and who consider refilling your batteries as a cheaper means of getting your old laptop back in order, this comment is for you. Beware refill services like or the like who promise a “quick turnaround.” If you are the type who needs your laptop for flexibility and needs it often, you are better off buying a new battery rather than wait the 2+ months some of these services take to work on your batter.

#15 lutz on 05.02.07 at 11:37 am

Thanks for the great tutorial!

Would you have any advice on how to pry the battery case apart?

#16 Jay on 05.03.07 at 12:59 am

I used some plastic tools made for prying cell phones apart. It takes a bit of technique to do it without damaging the plastic. I basically get one of the two tools in place, and then slide it along while using the other tool to keep pressure on the crack.
I used one very much like the following:

#17 Del on 05.24.07 at 5:48 pm

I replaced the 6 Li-ion cells in the pack for my IBM T40. I get great prices and service from I guess I need to reflash the chip in the pack. The batteries measure 3.6 volts, but they won’t charge in the laptop. It sees the battery pack and says it’s 1% charged, but won’t charge.

#18 Hack Your Laptop Batteries, Save Some Money « Geek News on 06.29.07 at 10:35 am

[…] […]

#19 eddyeddy on 07.23.07 at 2:31 pm

I thought doing this stuff to my X21 battery. The only problem is: I can’t even start because I’m unable to OPEN the battery case. It’s a tight seal. Did you find this in the X31 battery too?

#20 Jay on 07.23.07 at 4:44 pm

Yes, the two halves are sealed together very well. I used some plastic “cell phone opening” tools to gradually pry the sides apart, working the crack along as I went.


#21 Jay on 08.15.07 at 7:15 am

>I have a curiosity question
> which I wonder if you have ever considered or heard of
> elsewhere: Substituting lower cost NiMH cells for the Li-
> Ion cells.

While NiMH cells can be used in a battery, you should NEVER replace LiIon cells with NiMH cells. The reason for this is that the charging electronics in the battery are designed for LiIon cells, which are able to receive a much faster charge than the NiMH cells. If you tried to charge NiMH cells with a LiIon charging circuit, they would likely burst, burn, or even explode! Now, if you were able to find a battery pack that was similar to your notebooks (perhaps for an earlier model notebook in the same series that used NiMH batteries, you could replace the (LiIon) charging circuit with the NiMH charging circuit, and then you could use NiNM batteries.

#22 Christian Friedrich on 08.15.07 at 12:38 pm

Hi Jay,
which OS and/or which tool do you use to check the capacity?
Greetings from Munich/Germany

#23 Jay on 08.16.07 at 12:09 am

I’m using Linux (with acpi enabled) to get the detailed battery information.
cat /proc/acpi/battery/BAT0/info

>Hi Jay,
>which OS and/or which tool do you use >to check the capacity?

#24 Surf Boy on 09.26.07 at 12:45 am

I found a way to reset the full-charge capacity for Power Manager on WinXP. Follow instructions given by Jay, but perform a “battery gauge reset” between your full discharge/charge cycles.

An additional tip for this to work well is to fully discharge with all timers off, and then fully charge with the thinkpad switched off.

The results are:
– 1st reset: 8.76 to 12.73Wh
– 2nd reset: 12.73 to 13.33Wh (didn’t do something right????)
– 3rd reset: 13.33 to 18.62Wh
– 4th reset: 18.62 to 27.45Wh
– 5th reset: 27.45 to 37.23Wh
– 6th reset: 37.23 to 45.72Wh
– 7th reset: 45.72 to 52.99Wh??

Now my R51e runs for almost 4.5hrs before reaching 1% on “max battery life” settings! (I replaced the cells with 2600mAh!)

#25 Robert Stever on 10.02.07 at 9:22 pm

Can we do this with lithium polymer?

#26 Jay on 10.03.07 at 5:01 am

Lithium Polymer cells are basically LiIon cells that are more flexible, so should work just fine for this type of application.

#27 Jo on 10.24.07 at 9:01 pm

Jay, or anyone, do you know if there is a flash chip set in my Toshiba Satellite M45 S3553? thanks

Also tips for opening up the battery pack would be nice, thanks

#28 qad417 on 01.22.08 at 6:44 pm

hello! and do I can use the NiMH cells and just recharge it in outside recharger not in notebook?

#29 Jay on 01.23.08 at 8:36 am

QAD417: I do NOT recommend using NiMH batteries to replace Li-Ion cells. If you did, you could not use the built in laptop Li-Ion charging circuit. You would instead need to use a NiMH charger (either outside the notebook as you suggested, or somehow built into the battery pack). [Of course, if the original battery pack used NiMH cells, you could replace them with NiMH cells.]

#30 Nathan on 02.03.08 at 4:41 am

My battery at the moment has 4 3.7v (totaling 14.8) cells in series. There is space for 8 cells (there is a large capacity model that uses the same battery case). Could I create 4 banks (in series) of 2 cells (in parallel), still giving 14.8v but doubling the capacity. Will the charging circuit be able to cope? Will the battery me more likely to overheat (I guess the current drawn from each cell will be less so it will be cooler)?

#31 Jay on 02.03.08 at 3:57 pm


Technically, every cell should be controlled independently. (That is why your existing charging circuit should have a wire that goes to the connections between each cell to the next, so that it can control the charging current to each cell independently.)

However, as long as you stick with a matched set of cells, I expect that you should be 100% safe if you “doubled up” each cell (in parallel). To the charging circuit, it would look like each of it’s individual cells just got more capacity. You are also correct that the power draw from each cell would be halved so the temperature should be cooler. (I expect that your battery would also take twice as long to charge.)

You are indeed lucky to have a battery with extra empty space in it, what model/brand is your laptop?


#32 Nathan on 02.03.08 at 4:12 pm

Thanks for the quick reply? Now the battery is apart I can see there is only one wire to each pair of cells (actually to the connecter between the two). The laptop is an IPC Multimedia Desknote E (though I have seen it alternatively branded). The battery is an EM-G320L1 (I think made by Elitegroup Computing Systems).

#33 Michael Yaw on 02.06.08 at 4:58 pm

How do you open the plastic case of the Compaq Presario R3000 laptop battery, a 14.8V 6600mAH?
Do I have to cut it open?
Are there any higher capacity cells?


#34 Adam on 03.18.08 at 6:33 pm

I did a restore of my X31 battery and have soldered everything up correctly (looking at your pictures and ones I took before removing old cells) and the battery wont charge.
Watching the temps under linux show they stay normal but the charge/discharge rate doesn’t change. I left it hooked up for 20 minutes and nothing changes…should I just leave it longer?

#35 Jay on 03.19.08 at 8:58 am

Adam: It took me about 5-8 charge/discharge cycles to get my new battery charged all the way up (or at least, reporting that it was charged all the way up.)

It could be that the firmware/chip in your original battery does not allow the cells to be “replaced”, but my suggestion is that you run your laptop all the way down every night (and then charge it all the way back up) for a week and see if anything improves.

#36 Max Kessler on 04.02.08 at 6:28 am

Nathan, how did you open the EM-G320L1? There aren’t any screws and I don’t want to tear up the case by prying indiscriminately.

#37 Dom on 04.29.08 at 4:26 pm

I just opened up my laptop Battery (for Averatec 2300). The computer wont turn on with the battery. I left it plugged to the ac adapter for at least 4 hours, still the battery charge is at 0%.

With the battery case opened up, I can see each battery is at 3.8V, totaling around 11.5V. I even measured voltage at the connector :11.5V. The cells are still good! I guess it’s the flash chip. What can I do?

#38 Dev on 05.21.08 at 9:42 pm

Hi Jay,

My battery for my Sony Vaio is not charging anymore; so I decided to buy a new battery. The prices of the battery in Japan however is about $250.00, so I stated thinking about repairing the battery. Your explanation was clear and very helpful. Thanks very much. I am going to try and replace the cells. Wish me luck.


#39 Duc Tien on 05.28.08 at 1:07 am

Jay, I just replace 6 batteries in a Toshiba battery pack (quite a task when you have low quality soldering tools).

So far it is charging and has the power to boot up the laptop. Problem is… it is DRAINING LIKE CRAZY! I got 6x 2200mAH batteries and I believe the old ones were 1800ish maybe.

I’m about to do a 2nd full charge and see how it goes. Is this normal for the first few recharge cycles?

#40 Duc Tien on 05.28.08 at 1:57 am

Quick update:

Still draining battery for the 1st time but at 6% it doesn’t seem to down anymore.

#41 Jay on 05.28.08 at 9:19 am

Duc Tien,

If by “Draining like crazy” you mean that after the first charge the battery level indicator goes down rapidly (during the first discharge), then yes, this matches what happened to me.

The best I can come up with is that the charge control circuit thinks that it is still using your old cells, so when it sees a lot of current leaving the cells it figures that they are rapidly getting close to their “zero” point, and makes the percentage of battery left indicator drop appropriately.

In my experience, my laptop would continue to run for quite a while after the battery indicator reached the zero percent mark. (as in, 20-60 minutes!).

After several (5-6) full charge/discharge cycles, the charging circuitry eventually learns that the new calls were “better” than the old cells. (In my case, the battery capacity “increased” by about 10% each charge/discharge cycle.)


#42 Jay’s Technical Talk › Laptop Battery Refill update on 07.31.08 at 9:51 pm

[…] refilled the Li-ion cells in my laptop battery about 18 months ago.The battery has worked as expected since then. The only "special" […]

#43 Cesar on 08.14.08 at 1:02 pm

Hi, I repair a 336962 battery for HP. I changed all the cells, but when i put the battery on my laptop, the battery appears with a red X. What can I do?



#44 Jay on 08.14.08 at 2:17 pm


It is possible that your HP battery control chip does not allow cell replacement. Alternatively, the red X may go away after several charge/discharge cycles (if the battery is working correctly despite the red X).

#45 Martin Lee on 08.16.08 at 12:27 pm


I am interested in running a radio transmitter from a laptop battery (Model#BATCL50L) then recharging using the laptop. I am not able to find the battery’s output connection.

Is their an internal disconnect that is used when the battery is unplugged?

Thank you
Martin Lee
+1 408 898 4095

#46 mohsen on 10.25.08 at 4:13 am

Hi I have a DEll laptop. The batery keeps charge only 30 min. I bought the laptop about 1 year ago. Is it possiblefor me to repaire it?

#47 Jay on 10.25.08 at 6:14 am


I don’t know if the Dell batteries firmware allow the cells to be replaced or not. You will have to ask somebody who has done it for a DELL battery. (Or just try it yourself.)


#48 erdwi on 10.27.08 at 12:53 am

Hello Jay, thanks a lot 4 your valuable info. I wanna ask something:
1. How to determine whether the cell is death or still alive? Can I test it individually (in pair maybe)?
2. Is it OK to mix the new cell with the old one? (in case not all cells are die)
3. How to determine the problem is the cells or the charging circuitry?
Thank you Jay, maybe a bit too much questions eh? I’m sorry for that. Would you please send me a copy of your answer to my e-mail? I’m not always connected.

#49 Jay on 10.27.08 at 7:37 am


> 1. How to determine whether the cell is death or still alive? Can I test it individually (in pair maybe)?
You would have to test them individually. Charge the cell, and then discharge them through a load (motor? Lightbulb?) and watch how long it takes to drop X amount of voltage to estimate it’s current storage capacity. Obviously, if the cell does not hold a charge at all it’s completely dead.

> 2. Is it OK to mix the new cell with the old one? (in case not all cells are die)
The cells you use should all be at the same stage of life (either all old or all new). Otherwise your battery will only last as long as the weakest cell.

> 3. How to determine the problem is the cells or the charging circuitry?
Replace the cells. If it starts working, it was a problem with the cells. If not, it was the charging circuitry, replace that.


#50 erdwi on 10.30.08 at 10:21 pm

thanks a lot Jay, I hope you dont mind for more question. I want to test my old bat.
How can I recharge the battery without my laptop? can I just connect them to an adapter? If my battery is 3.6V what voltage should I set the adapter?
Thank you

#51 Jay on 10.31.08 at 5:53 pm


Unless you have a specialized Li-Ion battery charger, you should be very careful charging them directly (without going through the power protection circuit).
I use a CURRENT controlled power supply, and give them 4 volts at 50 mA (0.05 Amps) until the voltage maxes out (usually a day or so).

#52 RM on 12.05.08 at 4:37 pm

Hi Jay,

My battery only lasted at most 10 minutes so I decided to refill it. I used 2600 mah instead of the previous 2200 mah used. I read that the battery will only charge to 2200 mah. Anyway, the newly refilled batteries are working fine. Only one problem, the battery indicator is wrong. After the first charge for about 2 hours, I turned on windows still charging. It said 3% remaining when really it suppose to be 60% or so. The next day it said 4%. Today it says 6% left. I went through 3 cycles do far. Also when discharging, it said 100% , 99 … to 96 (for about 2 hours) then suddenly dropped to 7% critical battery. Could it be the internal flash chip in the battery needs flashing or something? Or it just needs more cycles?


#53 RM on 12.05.08 at 5:47 pm

Ok, I tried the command with ubuntu
Here are some lines.
So my battery is already fully charging and does not need cycles?

design capacity: 65486 mAh
last full capacity: 65486 mAh

#54 Jay on 12.05.08 at 8:36 pm

I would suggest putting the battery through several more full charge/discharge cycles. (The charge control circuit should eventually figure things out.)

The Linux /proc/acpi information looks promising, perhaps windows battery monitor also needs some quality time with the newly rejuvenated battery to figure things out.


#55 RM on 12.05.08 at 9:44 pm

Will the cycles damage the battery because of the discharging? I read that the life of Li-ion batteries lessen when discharged alot. Any way I will still try it. If none of these work, it has to be some chip in the battery?

So here is a summary from the previous cycle

When charging, charge completes at 6% remaining

When discharging, 100% to 96% is about 2 hours. Drops to 7% suddenly. 7% to dead is 30 minutes approx.

One other thing, when discharging, should I let it discharge until hibernation or take off hibernation and let it discharge all? Hibernation is at 2% so that may not be accurate on the battery timer at this time

#56 Jay on 12.06.08 at 8:24 am

You are right, discharging Li-Ion batteries all the way many times will negatively affect the lifespan of the cells. However, doing in five times (especially if you fully charge it afterwards without leaving it sit discharged for long periods of time) will have only a very small effect on the life of the battery. You’ll have to make a decision for yourself if having an accurate battery gauge is more important than eking out the absolute most life from your battery. (Also, if you never charge your battery to 100%, stopping at 90% each time the battery will last a bit longer.)

Re: Hibernation on low battery – Because the point of the discharge/charge cycles is to fix the battery gauge, it’s a good idea to disable hibernation for this procedure and let the battery go until it is fully dead. (You may find that the battery sits at zero percent for a lot longer than you expect….)


#57 RM on 12.15.08 at 10:12 am

Hi Jay,

Well, the battery never got better after more than 10 cycles. It never says more than 5% charging when it’s fully charged. I would really like the hibernation to work because it would just cut of when the battery is dead.

Do you know about reseting the battery. I saw a guide about opening it up and connecting a cable to a certain chip. The cable connects to the parallel port of the pc. The pc does the rest to reset the battery. Do you know about this? If yes, can you help me?

#58 Jay on 12.15.08 at 11:30 am

It sounds like your battery is set up to assume that the cells will never be replaced (so it cell life setting only goes down). Re-set information would be specific to your laptop brand and perhaps model, and I am afraid I have no suggestions.


#59 Frank on 12.20.08 at 9:32 am

I rebuilt the battery pack for a Dell Latitude C610 with a 66whr battery (rated 4400mah). The eight replacement cells were Tenergy, Li-ion 18650, rated 2600 mah. The results were disappointing. The old cells had a 50 minute life. The new cells last about 60 minutes even after six charge-discharge cycles. I expected 150 minutes. Secondly the new batteries cost about $70. A new aftermarket Dell battery costs about $105.

#60 Jay on 12.20.08 at 10:43 am


That performance sounds correct. Your original battery had 8 cells (arranged in four banks of two) for a 14.4v total voltage and 4400mAh total power rating.

Your new battery has 8 cells (again, in 4 banks of 2) for 14.4v total voltage and 5200 mAh total power rating. (Power/current is calculated by the cells in parallel, while voltage is calculated by the cells in serial.)

I would expect your new battery to last 1.18 times longer than the original battery (5200/4400 = 1.18; 50min * 1.18 = 59.00min).

However, if the 50 min life figure was from a “used up” battery, I would expect the new cells to do much better, and if they are not you may be experiencing a problem where the battery control circuit isn’t allowing you to “use” the full amount of power in the cells. Have you tried leaving the laptop on even when the reported power level drops to 0%?

#61 Frank on 12.21.08 at 10:38 am

You are right! With apologies to Shakespeare, the fault dear Brutus is not in the batteries but in the control circuit. By disabling the power management alarms under Windows the batteries can last upwards of 160 minutes. The power level drops steadily to 3% during the first 60 minutes then stays there for another 100 minutes. The alarm’s minimum value is 4%. Bother!

I tried booting Linux which gives more information about the state of the batteries. It reports that the “maximum” charge is about 30% of capacity. The voltage is a more accurate measure of the state of the charge. Apparently it is not used to estimate remaining battery life.

Various internet articles suggest that the control circuit can be re calibrated by letting the power drop to zero before recharging but that hasn’t yet worked for me. If it automagically starts to do so, I’ll let you know. In the mean time I won’t complain too much because I can now spend 2+ hours at the bagel shop before I have to look for an outlet. I just have to keep an eye on the power meter.

#62 Sorin on 12.21.08 at 12:08 pm

Hi Jay,

I tried repacking my toshiba tecra s1 laptop with (some) sucess. I cracked open the battery(opened very nicely) and i removed the old cells and replaced them with ones from a hp battery. I drained the cells, then mounted them exactly the same way as the old ones. One problem…the battery charges rrrrrealy slow (60% in the last 30 hours). Also it doesnt seem to want to run on battery, only works with ac adapter plugged in. Any advice ?

#63 azakki on 01.27.09 at 12:11 am

How on earth do you pry open ThinkPad battery cases? Awhile back, someone asked this question, and the suggestion was to use a plastic tool used to open cell phones. But how do you even get the plastic tool to work? I tried a mini flat blade metal screwdriver, but can’t seem to even get it into the seam, what more a plastic tool with a thicker blade. Even if you could somehow get the tool in, and then twisted it to pry the case apart, it seems that the plastic tool would break. Am I missing something?

#64 Jay on 01.27.09 at 7:45 am

It’s not easy to pry open the batteries. (I left a few pry marks on the side where I started.) You may need to start off with a very thin blade screwdriver. Once you have it cracked open a little bit, you push the plastic tool inside the crack, and then slide the plastic tool along the crack all the way around. It sometimes helps to have two plastic tools, one right after the other. Twist the one in the back to widen the existing crack, and push the one in the front forward to hold it open. Then move the one in the back farther up and repeat.

#65 RM on 02.06.09 at 8:50 pm

I have the exact problem as frank. The control circuit is not used to the new batteries so they dont report full life. 100% charging for me is 4%. Can letting the laptop cut of when the batteries run dry damage the laptop? It just cuts of when dead. The hibernation is of because of the 4% thing. Also the charging light is on for very long, like at least 5 hours. Can the battery be overcharging?


#66 M. F. Sherif on 03.19.09 at 10:58 am

I would like to ask two questions please.
I reconstructed an external battery pack for my vaio laptop with 6 Ni-MH cells serially 1.2 x 6 = 7.2 V
each one has 2400 mAh.
I connect this battery poles (+) and (-) separately to the corresponding ones on laptop battery location jack. I know I charge my battery outside notebook with an external charger. My notebook works good but there is no battery meter !
First: what are those poles on the laptop inbewteen (+) and (-) poles ?
they are not connected in my reconstructed circut, is there any hazard ?
Second: can I connect both batteries (my reconstructed one (Ni-MH 7.2V 2400 mAh) and that original one of notebook (lion 7.4 v 2600 mAh)) in parralel manner at the same time ?
Thank you.

#67 Jay on 03.19.09 at 11:18 am

M.F. Sherif:

The other connections between the Positive and Negative (ground) terminal are used by your computer to communicate with the charge & control circuit that should be in the battery.

Note that when you take a LiIon battery apart, it typically has a small circuit board that handles the actual charging and discharging of the batteries. This circuit ensures two things:
1) That the battery cells do not get charged “to quickly” and overheat, possibly bursting and releasing Hydrogen gas (and possibly burning or exploding).
2) That your laptop does not discharge the battery too quickly (also resulting in overheating, off-gassing, and possible fire/explosions)

Your laptop MAY draw power from a battery without a charge/control circuit, and it would probably be safe, but I would be very surprised if the laptop would CHARGE the battery before hearing an “everything is OK” signal from the charge/control circuit.

If the laptop DOES provide power to the battery (for charging) and you do not have a charge/control circuit, you risk the battery overheating and burning or exploding.

My major point: Do not use liIon cells without the proper charge/control circuit. The easiest way to get a charge/control circuit is by taking apart a broken battery (although sometimes they are designed to stop working once the battery cells are used up.)

As for your “in parallel” question. The correct way to add more power capacity to your battery is AFTER the charge control circuit. (i.e. put a new cell in parallel with each existing cell to double your capacity).

Note that (newer) charge control circuits manage each cell individually, so putting two cells in parallel where it expects one will work OK, but the two cells will be treated as a single cell, so they should both be of the same “age” when you start. If one cell is old and one cell is new, they will be mismatched and it won’t gain you much.


#68 simkard on 03.24.09 at 7:06 am

Hi !

I have a IBM ThinkPad X31 too and its battery is close to death (30mins of using on batteries).
I’m planning to buy some batteries, but as i found Ultrafire 3000mAh 18650 batteries on ebay, i’m just thinking of about gaining 6Ah of battery instead of 4.4Ah original capacity.

What do you think of it ?
As the cells capacities are superior than the original ones, it would logically not be a problem for the electronic embeded into the pack to charge them fine.

Waiting for your advice to get the right decision.

#69 Jay on 03.24.09 at 8:58 am


Original X31 batteries were rated at 4.4AH (using pairs of 2200mAh cells). New X31 batteries are usually rated at 4.8ah (using pairs of 2400 mAh cells). You are correct that 3000mAh cells would theoretically give 6Ah of capacity.

However, this is the first time I’ve seen 3000 mAh 18650 batteries, and since I can only find 3000mAh cells listed on Ebay, you should confirm that they are indeed rated as 3000mAh batteries according to industry standards. (Many cells will do better than their rating at the beginning of their life, but typically cells that are rated as “2400” or “2200” mAh are guaranteed to provide that capacity for a certain number of charge cycles, etc. These 3000 mAh batteries may just be 2600 mAh cells that happen to give 3000 mAh on the first few charge/discharge cycles, but are really no better than 2600 mAh cells. [Or, they could be a brand new cell that is just better than older ones…]

The link you sent advertised them as having “short-circuit and over-current protection”, so they may already contain charge control electronics that you would have to remove before using. I have found 4pc of 18650 @ 2600mAh for $25, so the $35 price seems appropriate.


#70 Sanford Scholton on 04.05.09 at 12:22 am

My battery is fine. It just won’t charge. Apparently a diode on the motherboard has closed and the AC circut doesn’t work. laptop works fine on battery. just can’t get it to charge. Have you ever made an external battery charger?

#71 Jay on 04.05.09 at 10:18 am

I have not built an external charger, let us know if you get one working.

#72 Timothy Riddles on 05.06.09 at 8:21 am

Hi there, thank you so much for this site. I have a Ibook Rechargeable Battery Model M8403. Please advise if it will be possible to repack this battery and where i can get the cells. I reside in Cape Town , South Africa.

Thank you and God Bless.


#73 Bardh on 05.18.09 at 9:06 am

About the battery chip, I have an idea,
will it charge if we don’t actually disconnect the old battery pack until we put new cells.
The idea is to open the case, remove all old batteries together with electronics,
put new cells into the empty case and parallely connect new and old cells, only than when electronics are wired with the new cells disconnect them from the old ones. I’m not much of an expert but theoretically I think they should work?

#74 Jay on 05.18.09 at 11:39 am


By doing this (carefully swapping in the new cells) you could keep the charging chip from realizing that the cells had been changed. However, the chip may keep an internal variable that keeps track of how much power is “left” in the cells, and every so often it will decrement the variable, but it is never allowed to increment the variable.
So, depending upon how the programming works, you may or may not be able to get more performance from your “new” battery. Try it out and let us know how it works.


#75 jatin on 05.31.09 at 4:19 am

I’ve replaced the cell of my laptop (IBM ThinkPad R51 2887 MQ6) accourding to your suggestion, Now my laptop is not running on battery ( it runs well on AC power ). in IBM powermanagement software it shows that battery is in good condition but amp-hour is 0.00 , what happened to it?? will you suggest me what should I do now…

#76 Jay on 05.31.09 at 8:06 am


Things to check:

1) A wire is not correctly connected and one or more of your cells is not currently connected to the power circuit. Open the battery up again and look for loose connections and make sure all of the solder joins are good.

2) Try the battery in a different laptop. and try the laptop with a different battery to isolate the problem to the battery or laptop. (I’d expect the problem is with the battery, but you never know…)

It is possible that your particular battery has a power circuit that does not allow refills. If you find the solution to your problem, please let us know.


#77 jatin on 06.02.09 at 11:50 pm

I’ve check the connections of the battery is looks like all is good …. but now I find out the problem, there is a EEPROM in by battery pack which contains the data for my battery now I need to reset that EEPROM … I’ve Linux script to reset the EEPROM ..I’ll try to reset it this weekends


#78 Jay on 06.03.09 at 6:34 am


Good to know that a software fix exists. Can you post a URL for where to find the script?


#79 Jan on 06.21.09 at 5:58 pm

Hi, I just replaced my 4 cells in a Thinkpad X60 Battery. I have a similar problem as Jatin:
– Laptop doesn’t start from battery
– When the power cord is connected, the battery sign blinks orange
– When starting the computer, battery status informs that “irreparable dammage”

It seems that while rebuilding the cell, the chip’s error bit was set. There are programms to reset Eeproms of SMBus based battery packs (AccPlus, SBWorkshop). I was wondering if it’s possible to use an Parallel port to SMBus adapter and reset it with Linux Software.

Does anyone know the pinout and specifications of thinkpad battery connectors?

#80 Tim on 06.23.09 at 11:19 am

Thanks for the interesting story. Just curious: why do the cells need to be soldered? Can they be used touching (under spring tension), safely?

#81 Jay on 06.23.09 at 3:06 pm

LiIon cells do not typically have “nubs” at the top like a standard AA battery, so pushing them together will not necessarily make electrical contact. (Plus, laptop battery cases do not have springs.)
If you made sure that each battery had good electrical contact with the next one, and had a spring to hold them under tension, I see now reason you could NOT hold them together with springs, but I suspect that a soldered connection has better electrical properties.

#82 Paolo Del Bene on 08.26.09 at 10:33 am

hello, i got a thinkpad t23, the batteries
are the same, the red ones.

I need of 10,8 Volt and 4.400 mAmpere

please can you tell me the correct URL to watch ? and the other part of the URL which is ?

awaiting your reply,


#83 Jay on 08.26.09 at 11:41 am

You can purchase any of the 18650 batteries. They come in various different capacities and costs, but any 18650 battery will physically fit.

#84 Josh Spradlin on 09.10.09 at 5:19 am

I haven’t tried it yet but, I think a spark plug gapping tool might help to open up the battery packs a little.

#85 Come possiamo recuperare batterie che hanno perso capacità? - on 09.28.09 at 6:29 am

[…] sono quelle fatte a macchina con saldatura a punti. vedi qui, un esempio da cui mi sono "ispirato": Jay’s Technical Talk � Refilling laptop batteries! comunque io sono andato bene, alla fine la batteria dura 40-45 minuti (prima non durava 3 minuti). […]

#86 GDH Press: Blog » Reparo e reciclagem de baterias de notebook on 11.03.09 at 2:20 am

[…] […]

#87 Joe P on 12.08.09 at 8:04 pm

For those of you who are having probs with your new packs not charging. Most smart chips memory is erased when power is lost and therefore wont charge anymore. Never disconnect power from the chip hook up a secondary source with a 100k ohm resistor and dont remove it until your new pack is hooked up to the chip.

#88 Clive Cussler on 01.03.10 at 5:54 am

Before removing my old cells, should I make sure they are empty? If I remove them when they are supposed to be fully charged is that a problem?

Also, if I get 2600mAH cells instead of 2400mAH ones like those in my battery, will I get a battery that lasts longer or am I just going to waste money because the laptop will treat them as 2400mAH cells anyway?

#89 Jay on 01.03.10 at 7:38 am

Li-Ion Cells store best at around 40% charge. If you are just going to throw them out, you could discharge them lower than this, but I don’t see a big point in doing so. Assuming you recycle them in a proper battery disposal location, they will know how to handle them correctly, charged or not.

If you purchase better (higher capacity) cells than you currently have you should get a better (longer) run-time.

#90 Clive Cussler on 01.03.10 at 8:30 am

Hello Jay,

First of all, thank you for your quick answer. I was afraid it would take days to get a reply, but a few hours after sending my message I checked your site again and here was your reply. Thank you!

I guess I didn’t explain myself properly about discharging the cells or not before removing them. What I meant is before putting new cells in my battery is it better to have the old ones fully charged so the electronics on the battery will see the cells as 100%? Does is make any difference at all if the old cells were at 100% before being removed? Hopefully, this is clearer this time. :)

#91 Jay on 01.03.10 at 8:33 am

The electronics will have to re-adjust themselves to your new cells over the next several charge/discharge cycles, so where the old cells were shouldn’t matter.

#92 Yes on 01.13.10 at 4:36 pm

Thanks for your infos jay !

And sorry for saying: Appearently most of the people here have BY FAR NO idea of how dangerous this “soldering around” is in fact. BR

#93 Kham from NZ on 01.15.10 at 8:29 pm

Wow, almost 2 years and still replying to comments :) Well done. I have recently needed to hack laptop batteries and this site come up in a search. I needed a really long runtime and got it. I was fortunate enough to get hold of some New Old Stock cells for cheap. 20Amp Hours on a IBM T41 goes a long way, unfortunately it does not fit in the original case. I can share a trick to opening up some packs, use a sharp hobby knife/craft knife/boxcutter to cut a wider slot at the seam so you can fit your tool in to start prying.

#94 Mastertje on 02.03.10 at 5:49 pm

Hey man,

I just did your little trick on my nearly 4 year old fijitsu siemens pi1536 and it worked perfectly!!

First time it charged in little over an hour, and I then proceded to run battery eater pro v2.70 when it said I had just 20 min over battery time :( But it stuck at 7,4% and it’s still there now after an hour of hardcore processing. So I’m a very happy man!

By the way I had huge difficulty getting the batteries out without destroying the cartrige, which I ended up doing. But I taped somthing up and now I’m home free :)

Thanks again!

Greetings for The Netherlands.

#95 tejas on 08.29.10 at 9:19 pm

Terrific post! I had read this before and just revived my old Averatec battery with cells from my wife’s Dell. It works great!

Interesting point about the gradually increasing capacity. I have started off at 1236mAh and will see if I can work it up all the way to 4400mAh.

PS. You might remember me from GSC at Tech.

#96 Jay on 08.30.10 at 7:28 am

Hi Tejas!

It’s not so much increasing capacity, as getting the batteries power electronics to recognize the improved capacity.

#97 tejas on 08.30.10 at 12:01 pm

Hi Jay!

Ubuntu refuses to discharge my laptop all the way, so initially the capacity refused to increase. However, I discovered that the laptop’s BIOS has a “battery calibration” feature where it does a full charge-discharge cycle, and bumps up the learned capacity.

I guess this is similar to Surfboy’s situation above (#24), where he ended up using Windows’ Power Meter.

#98 Omid on 09.01.10 at 7:43 am

Hi Jay
Good on you for your patience with this many questions answered over so quite a few yrs.
My question:
I’m about to rebuilt my Dell Latitude D620 6 cell pack.
However, here and there I read that I should use “Unprotected” cells for replacement.
I have even seen recommendations to REMOVE the protection circuit from each cell before inserting and connecting them, in case one is using a “Protected” cell as replacement.
The rationale is that the pack’s built-in protector and the cells’ protectors might not like each other and cause conflict.
On the other hand when I look at the OLD cells they clearly seem “Protected” as I can see the notch at one end of each cylinder as well as a stripe along the cells, running underneath the shrinking wrap.
Now could you please shed some light on this issue and get me out of this confusion?
Thanks in advance

#99 Jay on 09.01.10 at 8:52 am


My laptop had “unprotected” cells, and I replaced them with the same.

If your laptop is using a cell with a built in protection circuit, my advise (with no real knowledge to back it up) would be to replace them with the same thing.


#100 Lex on 12.01.10 at 1:24 pm

Jay, I’ve been trying to refills thinkpad T42 batteries, but no luck. I cut the cables from the controller to all the cells, and re-create exact cabling with new cells. After that reconnecting the cells with the controller.
Did I make a mistake here?
Should I keep feeding the controller with some voltage while replacing cells one by one?

#101 Jay on 12.01.10 at 2:20 pm


I was successful with refilling a “replacement” x31 battery, that was not manufactured by IBM/Lenovo. It is possible that “official” controllers will self destruct if you un-hook them from cells/power.

Trying to hot-swap the cells without removing power to the controller at any point should work if you are able to do it successfully. (Indiana Jones music in the background…)

#102 Julian on 12.05.10 at 5:50 am

Hi Guys, Iv done a Repack for my Toshiba notebook (Battery pack: PA3479U) and I had the problem of not charging and the pack was not powering the machine at all, because I disconnected the controller board. What I did to “reinitialize” the controller to accept charge and power the machine was to manually discharge the pack to about 3.1v per cell with the controller connected. After doing that the pack started low level charging until the cells were with in spec of the controller to allow fast charge. Now the pack works 100% and I am quite happy with my handy work.

P.S. I used lithium polymer cells and I now have 8800mah of battery from the old 4400mah:)


#103 Jay on 12.05.10 at 8:58 am


Thanks for that tip, hopefully the same procedure will work for other battery controllers from other laptop brands!


#104 Patrick on 01.25.11 at 2:56 pm

I have looked at a couple battery suppliers and the 18650 cells all seem to be rated at 3.7 volts now. I know I need three 3.6 volt cells to match my battery pack which has a 10.8 volt output. Will this work if I use 3 x 3.7 volt cells for a 11.1 volt battery output? Is my laptop going to blow up from this 0.3 difference in voltage?

#105 Jay on 01.25.11 at 8:46 pm


I believe your laptop will be fine. Typically electronics allow for at least a 10% variance in the voltage levels.

#106 Standard Battery everywhere « couchcricket on 02.11.11 at 9:18 pm

[…] will consider breaking open my laptop battery and see if I can fit the standard Li-ions but have not yet tried it. This is just a comparison of […]

#107 Reparo e reciclagem de baterias de notebook « Dica do Notebook on 03.07.11 at 8:10 am

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#108 ancient1 on 03.15.11 at 9:42 am

Hi Jay

I got a wierd situation here , HELP !!

– Just opened the battery (GA-M912M netbook ) : P/N 92BT0020F.
– I see 4xCGR18650CG [MH12210] cells (Panasonic) , rated at 2200 (avg). 3.6V.
– 4×2200 = 8800mAh
– But the Battery is rated 4500 !!!!
4400 = half 8800. usually a manufacturer would rate at lower to be on the safe side…

So what do I do now ? and how would you suggest I go about dis/connecting the new for the old ?

and i forgot … it 7.2V (2×3.6V) 4500mAh .

Thx a bunch for this page ! 2011 and still going .. :)

#109 Jay on 03.15.11 at 11:30 am

It sounds like they have 2 pairs of 2 cells. Each cell is wired in parallel with another, and then the two pairs are wired in series. This gives 7.2v total (2×3.6) but it also doubles the individual cell capacity (2200×2 = 4400). I expect that the battery is rated at 4500 because the 2200 rated cells actually give 2250mAH each, so 2250×2 = 4500 mAh.

As long as you keep the connections exactly the same, you should be able to replace each cell with another 18650 style cell and have everything work.

Depending upon the battery charging/discharging circuit….Some people have commented that you should never remove power from the circuit while replacing the cells. So, insert the new cell before removing the old cell. This makes it so that the battery management circuit doesn’t know that you’ve replaced the cells. This keeps it from shutting down…but many battery management circuits don’t care…that behavior varies from brand to brand…

#110 Hoon on 03.18.11 at 8:49 am

Hi, I opened up my thinkpad x61t 8 cell battery pack. This is made of two strings of 4 cells, total 8 cells. 4 are 18650, and the other four are rectangular ones. But I couldn’t find any rectangular cells anywhere(about 50x35x9, by eyeballing)

Anyways, I decided to just replace the four cylindrical cells, which are 18650. I’m thinking of putting in 2600mah LG cells. Costs $38 including shipping. My current battery holds about 62% of original capacity, and I’ve done the calculations. If I replace only one string cylindrical cells and all goes well, I’ll still end up with 108% of original design capacity. Would it be worth it? I’m not too worried about only replacing one string because I think they are controlled separately from each other.

One more question, to feed the voltage while replacing cells, I’m planning to use a voltage/current generator. Should I use 4.05V as each individual cells currently measure, and replace one cell at a time, or should I provide 16.20V for the entire string and swap the whole string at once? I’m thinking I need to do 4.05V, and replace the individual cell one by one, because they each have wire connection to the circuit board for individual measuring voltage.

Another question, what current should I be using? 50mA?

By the way, I read those ebay 3000 mah 4000 mah battery are bogus and they are junk.

#111 Jay on 03.18.11 at 10:19 am

As long as the two strings are able to “share” the load, replacing one of the two strings should still increase your battery life. I think you will need to provide power and replace cells one at a time. (Typically most battery management circuits have a small “sensor” wire that goes between each pair of cells, and you need to keep the proper voltage on that wire as well as the series “power” wires at the end.) I have no idea what current you need to provide. I expect that you would only need 50mA to trick the BMS chip into thinking the cell is still there, but it would not hurt to use the full rating of the max current that the cells can provide (as long as you don’t accidentally short your wires!)

#112 jayvirus on 03.22.11 at 7:10 am

hey,nice i’m planning on building, my battery is a 6cell and i’m having trouble finding the correct size, they are the same colour as the ones in the photos(or look the same) what model number are your replacement batteries?

#113 Jay on 03.22.11 at 8:00 am

My cells are standard “18650” cells. You can buy them with various different mAh ratings. You probably want to pay extra for the largest you can find if you are going to go through the effort of replacing them. (Or perhaps buying one size smaller than the largest, as sometimes the largest capacity cells charge a premium.)

#114 Tauseef Masood on 06.21.11 at 3:01 pm

Hello My Jay..
I’ve 12 Cell Ultra Capacity Battery of HP… since a month back it is giving me trouble i.e. it is not charing more than 100%, just it stuck on 40% and then after few time stop on 44%…
Now i already opened the Battery Case and found that there is some Samsung 2200mah batteries installed.
I searched a lot on internet and found that i can get each battery at a cost of $6…… for the same 2200 MAh.. because the HP battery check make report that Battery Capacity = 6600 MAh… so i think that if i’ll go over this 2200 mah capacity i’ll not able to get proper working of the battery….
also guide me that if there is any Flash chip installed in this battery so if there is any i can rather go to buy another 12 cell ultra battery instead of Cell replacemnt..

Kindly update me on my email also..

Tauseef Masood

#115 Jay on 06.21.11 at 3:39 pm

If you are going to replace the cells, you can either replace them with the exact same power level, or buy slightly more expensive cells to get more capacity. (I recommend spending a little more money to get slightly higher capacity cells. The amount of work is the same regardless of the capacity of the cells you buy, and it’s a good amount of work, so you may as well get as much benefit as you can out of it.)

Even if the electronics think they have 2200 cells, if you substitute 2400 or 2500 or 2600 mAh cells you will probably find that you can make use of the extra capacity (even though the power control electronics may be slightly confused, and report that you are at 0% battery remaining for a half hour or so before the battery is fully used up). Charging it usually regulated by voltage and current draw, so it will charge up the cells fully, even if they are somewhat larger that it is expecting.

Unfortunately, I am not familiar with that specific battery, so I do not know if the chip is programed to “die” when/if you remove the cells. The safe thing is to connect the new cells before removing the old cells (so the power electronics never “notice” that the cells were removed). This takes a bit of effort, but is the only way to be 100% sure that the replacement will be successful.

#116 Tauseef Masood on 06.21.11 at 3:59 pm

Thanks for your quick reply…

How I can connect the new cells before removing old? Do u have any video or information to share?

Any help will be batter…

#117 Jay on 06.21.11 at 4:10 pm

My recommendation is to solder the new cells up in the same
configuration as the old cells. Then, solder a wire from the new cells
to the power control chip in all the appropriate places.

(basically, the new cells and the old cells will be in parallel)

Then, cut the wires that go to the old cells after the new cells are all
hooked up. As far as the power control electronics know, the cells were
never unhooked.


#118 mashal on 10.18.11 at 1:52 am

Dear Jay.

I Live in a city where about 90 % percent poeple purchase usde loptop computers, which usually imported from European countries. there model also used to be out dated , in which the majorproblem comes with batteries, which literally do not provide sufficient back up. I have very much interest in this repairing work, and I want to learn it properly. therefore , I need your kind advice.
If I start learning this repairing work, can I do? As I have no experince indeed in this work. And for the purpose what exact tools are required for my workshop?

Looking forward for a positive response.

#119 Jay on 10.18.11 at 6:12 am

You can do it, but it will take some practice and learning before you get good at it. Also you should know that some batteries are not easily refillable due to their control electronics not accepting new cells.

For tools you will need some screwdrivers, a plastic separation tool
(plastic prybars, blade, dremel with saw blade, etc) plus a soldering
iron. (Ideally you’d have a li-ion welding machine if you plan on doing
this a lot, but they are more specialized.)


#120 Guy on 11.09.11 at 6:16 am

Hi Jay,
just for the record-I have HP Compaq 610 and the new battery (2600mhz Samsung) works ok for 3.5 Hours !!
(original works with 1 hour on full brightness).

My problem is that the battery bar show 0% after only 12 minutes! and if I shutdown when batt on 0% the computer do not open again, just until I plugged it again.

Maybe when the batt is on 0% the chip on the batt do not let the computer to start.

I’ve tried to charge it to 100% and discharge it fully (in linux) so the computer shutdown in a moment with no hibernate, but it didn’t calibrate my batt.

Now I don’t know what to do,when I want to use the computer I have to:
1. charge it full.
2. open on linux
3. wait 10 minutes to discharge to 0%
4. restart to win 7 and have about 3 hours of working on 0% with no time bar.

Do you have another solution?


#121 Jay on 11.09.11 at 8:08 am

It sounds like you have successfully replaced the cells, but the power management chip is not “learning” about the new capacity. When I replaced my cells I had to do full charge/discharge cycles 5-7 times, and my chip gradually learned about the new capacity. If your chip is set up so that it will only allow capacity to go down (and never “grow”) you will never be able to get a good capacity measure on your new battery. Hopefully you will be able to modify power settings in your OS so that the OS does not shut down automatically when the battery (falsely) reports a low reading.

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#123 Donald Roberts on 01.21.12 at 12:20 pm

if your system wont run on the battery or the battery wont charge after doing this it might not be the flash there are fuses on the motherboard that blow sometimes when you replace the batteries due to them being weak and after you do this they cant handle the full power…so replacing these have fixed the issue for several of the laptops that have been brought to me after they did this and thought they messed something up…they didn’t so i say check the fuses and rule out everything before thinking its a flash issue

#124 Ammy on 02.07.12 at 3:38 am

Its okay that we can change the cells of a laptop battery,
but can we increase the number of cells in parallel to give long backup time with same output.
a battery of 6 cells with 11.1V at 4400mAh
increased to 9 cells with 11.1V at 6600mah
the output will be same but the work hour will be increased.
I have a doubt that it will harm ma laptop…so please clear ma doubt…..i have Dell Inspiron N5010 Laptop

#125 Jay on 02.07.12 at 10:13 am

You should be able to add extra cells in parallel to accomplish exactly what you want (Extend the amount of time the battery can power your laptop.) It will take your laptop longer to charge up (as the electronics are going to limit the charging current as if it still has 6 cells instead of 9) but that actually means that you will be charging each cell slower than normal, so they won’t get quite as hot when charging. (They also won’t get as hot when discharging, because each cell is providing less power at any one point in time.)

#126 Ammy on 02.07.12 at 10:21 am

I do not bother about the charging time it takes to charge i can give as much as it will, jus i want is long backup so by doing this jus i want to confirm that the battery i am going to use or the laptop will not be damaged.

#127 Jay on 02.08.12 at 1:00 pm

When opening a piece of electronic equipment and soldering extra things to it you always have the chance of damaging it, but unless you hook something up incorrectly I expect that it will work fine. Even if you mess things up, it is more likely that the battery will stop working than you will actually be able to harm your laptop. The biggest problem I see is how you will physically mount the extra cells to the battery so that you can still plug it into your laptop.

#128 John on 02.11.12 at 7:15 am

Your project is very good I would like to use for my netbook s10-2 that after 2 years the battery is almost dead (when i bought it has 15% treadwear).
The cells that is build with are samsung icr18650-22f, so I have to choose new 18650 cells with 2.2Ah?
My other question is that the cells are not attached to each other and to the controller with wires but with flat metal (i don’t know how to describe it) and the problem is that I want to solder the new cells before removing the old ones (for the memory). Can I use any other simple wire???

I will buy cells from an internet shop from China so I want to know how can I test the new cells that are not DOA

Thank you!!!

#129 Jay on 02.11.12 at 12:41 pm

You can use any 18650 cells that are 2200 mAh (or greater if you want more capacity). You could possibly even use cells of a smaller mAh rating, but they may be charged slightly too fast and heat up more than is recommended.

Due to the amount of work involved, I recommend paying for the largest capacity cells you can buy that are not outrageously expensive. The flat metal “thick foil” is used because it is easy to weld to the batteries, can be folded to get the batteries very close together, and is inexpensive. You can use any wire as long as it is able to conduct the same amount of energy as the metal foil. (My old X10 laptop takes 10-13 watts of power from the battery, newer larger laptops may take more.)

The only real good way to test cells is to charge them up with a voltage/current controlled power supply, then discharge them to make sure they have full capacity. This takes time and somewhat specialized equipment. In your case, as long as all of the cells have a similar voltage level when they arrive, they are probably good to go.

#130 shkence on 02.16.12 at 7:06 am

Great, thanks guys,

any advice How to know if flash chip is present on battery, would be very helpful.

thanks again, looking forward for any explantion in regard to my question

#131 Jay on 02.16.12 at 9:29 am

You really won’t know if your batteries charging circuit will “die” if you unplug the cells until you try. If you have read reports of other people easily replacing cells in the same brand/model battery before yours is probably safe. If you have no idea, you may want to connect the new pack in parallel with the old pack and then disconnect the old pack. (When doing this, you want to watch out for the new pack overcharging the old pack when they are connected, so make sure you charge the old pack (or discharge the new pack) so their voltages are very similar.)

#132 on 02.25.12 at 11:43 am

Thanks Jay, It really helps, I will try and let you know, thanks again.

#133 Gavin M. on 03.13.12 at 2:16 am

Hi, very nice write up. I did this to my Vaio battery, but now it is not detected by my laptop at all. I think the circuit you were talking about is not allowing current from my batteries past it. I know the batteries are charged, I checked them. Thanks.

#134 Jay on 03.13.12 at 9:09 am

It does sound like perhaps the VIAO battery has a “self destruct” code that keeps it from working after it detects that the original cells have been removed.

#135 Gavin M. on 03.16.12 at 1:04 am

Thanks Jay. Any way to bypass this? Or did I just waste all that money on new 18650 batteries?

#136 Jay on 03.16.12 at 3:10 am

You may be able to “reflash” or “reset” the chip, but I wouldn’t know how. You’ll have to do some / a lot of research about the specific battery charging control chip used in the circuit board on those batteries. That isn’t impossible, but unless somebody has already figured it out for that specific battery type, it will take a lot of work to figure out.

For others doing cell replacement with your type of battery, it sounds like they should build up the “new” battery pack out of the new cells, then connect the whole thing “in parallel” with the existing (but very old) battery pack of “old” cells, and only then disconnect the old cells. (You’ll want to make sure that the new cells are charged to about the same voltage as the old cells so lots of current doesn’t flow one way or the other. The easiest way would be to charge all cells before connecting.) This way, the monitoring and control chips don’t notice the swapout.

In my case, I actually replaced cells in a “generic” laptop battery, and apparently the generic battery manufacturer didn’t think it was critical to prevent people from replacing the cells. (Just like generic ink cartridges allow you to refill them…)

#137 Gavin M. on 03.16.12 at 3:37 pm

What I’ve found so far is that the negative battery side is getting all the way to the main negative pin. The positive side is not allowed to pass to the positive pin. I soldered in a wire directly from the pos. batt. side to the pos. pin and it did actually power my laptop, however my laptop still didn’t detect the battery therefore was unable to charge it. So that wouldn’t work. What I really need to find on this battery is a pin out diagram. No luck so far.

#138 Ramesh on 04.18.12 at 2:11 pm

Hi, Jay
This is Ramesh, I need some information from you.
I am having HP HDX16 note book since one year without no problem. Usually my computer getting heat in normal use, and when i am working with video editing , it will get more heat, but I never considered that heat because of I checked my processor graph as 99 percent when in editing mode. Recently battery stopped working suddenly, but its showing as 29% available and plugged in charging, but when I removed power card computer getting off. why?

My question is what was problem with battery?
Why computer is not using remaining 29% power?
Gradually decreasing power in the battery to 27,26,25% why its not charging?
I like to replace the cells is it possible?
I cant able find cells in our country market, can I use any LI.3.6 cells from other brand battery or same HP DV4 battery(my battery model same like as DV4battery model) 10.8v, 55w
If I want to replace how to check cells condition, can you give me some guidelines in the refilling the battery

Thank you

#139 Jay on 04.18.12 at 6:49 pm

It is possible that a thermal cut-off switch inside of your battery has tripped (due to the overheating when video editing).

I don’t think that this indicates a problem with your individual cells, so replacing them may not fix the problem. First thing to try is to remove the battery from the laptop, and turn the laptop off, and let them both cool off overnight. Hopefully the thermal switch will re-set (and it’s not a fuse that is blown forever). If it never re-sets, you may need to purchase a new battery.

#140 usha on 05.01.12 at 1:27 am

Thanks Jay for this nice tutorial. After reading this I decided to give a try on my laptop’s battery, which has been dead for 3 years.

My laptop is Mitac8640M4 model. Which looks very similar to winbook laptops. The battery pack is made of by Panasonic, model CGR-B/T19SE-MSL (14.8V – 6000mAh).

There is no battery indicator on task bar, but in power option properties it shows a red cross mark on a battery and 0%. When I remove the battery pack it shows not present.

All I want to know is that, is the circuitry still working or not (3+ years not working)? Can I use over 6000mAh cells like 6600mAh or 7500mAh cells or lithium polymer pack?

Waiting for your expert opinion.

#141 Usha on 05.01.12 at 4:51 am

Thanks Jay for this nice tutorial. After reading this I decided to give a try on my laptop’s battery, which has been dead for 3 years.

My laptop is Mitac8640M4 model. Which looks very similar to winbook laptops. The battery pack is made of by Panasonic, model CGR-B/T19SE-MSL (14.8V – 6000mAh).

There is no battery indicator on task bar, but in power option properties it shows a red cross mark on a battery and 0%. When I remove the battery pack it shows not present.

All I want to know is that, is the circuitry still working or not? Can I use over 6000mAh cells like 6600mAh or 7500mAh cells or lithium polymer pack?

Waiting for your expert opinion.

#142 Jay on 05.01.12 at 1:25 pm

It sounds like your battery charging circuit is still working (and talking with the laptop) as the display changes from “bad cells in the battery” to “no battery” when you remove it. You should be able to replace the 6AH cells with 6.6 or 7.5AH cells without problems, although charging will take a slightly longer amount of time (but discharging should also last longer as well ;>). If your battery protection circuit is designed to “shut itself down” if the cells are removed, you may want to solder the old cells in parallel with the new cells, before disconnecting the old cells. This way the battery protection circuit may not know that you have made the swap.

#143 Usha on 05.05.12 at 7:15 am

Hi Jay

Thanks for your reply. Once again I need your advice. I’m having hard time finding right kind of battery cells. I was searching the net for 6.6 or 7.5 AH cells. Though I find some but don’t know what would be the right voltage for me. Because there are no voltage sign on the battery cells. So, how to determine what is the right voltage for me. As the battery pack says (14.8V – 6000mAh). I have 12 cells altogether in my battery pack.

#144 Jay on 05.06.12 at 10:22 am

All battery cells of the same chemistry have the same voltage, so typically websites don’t bother listing the voltage. If you have 12 cells overall, and the battery pack is labeled as 14.8 volts and 6000 mAh, it sounds like you have 4 sets of 2 cells in parallel. LiIon cells are typically around 3.2-3.7 volts (nominal, they go higher when fully charged and lower when fully discharged). So a set of 4 cells in series is 14.8 volts. Because you have sets of 2 in parallel, each cell is actually only half the Ah capacity, or 3000 mAh. So you are looking to replace them with 3000 mAh (or 3Ah) cells (or similar…)

#145 Tom on 06.08.12 at 8:23 pm

Just replaced a Thinkpad T400 6-cell battery and it is totally not worth it. Don’t know if it works yet, will plug it in later, but the problem is first, the case now doesn’t shut completely, the front of the batter doesn’t (other side of the connector). Replacing the cells was a nightmare, there was only one short 2-inch wire and everything else was the flexible sheet that is soldered to the battery that wouldn’t come off. I don’t think its worth it, yes if the battery works, I will try to get at least 2 years out of it, will probably use black duck tape to keep the case completely closed.

#146 Jay on 06.08.12 at 8:47 pm

Yes, it is definitely a lot more work/time/value than just buying a replacement battery. If you are good with the assembly you can make everything fit, but unless you know the BMS control board inside allows cell replacement you have no guarantee that it will work until you try it out.

#147 Tom on 06.08.12 at 9:11 pm

I think the either the plastic has changed or the design has changed in such a way that putting them together is a lot harder now. I don’t there was any way of taking the case apart without destroying some of the plastic there is required to snap the case back together. I will find out later today if it works.

#148 Tom on 06.12.12 at 12:41 am

Looks like the battery is dead, won’t charge at all. I have the Thinkpad T400, I wonder if the battery died when I took the cells off. Well probably did, I know I soldered the batteries correctly, though there are more wires than usual.
Any suggesting, besides checking if the wiring is good. Is there to check if the electronics stopped working when I took the batteries off line.

#149 Jay on 06.12.12 at 6:49 am

If your battery is “stock” IBM/Lenovo the BMS electronics inside are likely to turn off if any of the cells are removed. (Some people have reported that by soldering the new batteries in place before removing the old batteries they have successfully handled the “hand-off” without disabling the built in BMS board. However, if you do this you have to be sure that the old cells and new cells are very close to the same voltage so that not too much current flows between them when you connect them.)

If you have a generic replacement battery, the BMS boards are less likely to shut off just because the cells are removed as part of a replacement.

Before you give up on it, leave it in your laptop for a few days, rebooting and/or shutting off your laptop for a few hours every day/overnight, it is possible it will reset itself.

#150 shkence on 06.17.12 at 3:00 pm

I appreciate very much your explanations. :)


#151 shkence on 06.23.12 at 4:48 pm

Hi Jay,

I replaced my battery cell on my laptop dell D 610. All look great , my battery lasts more than 2 hours, only the timer gets confused, and the charging flash light in my laptop blinks in red; no matter charging or when is fully charged, it doesn’t stop. I can’t understand what’s wrong? Any advice from you. thanx again

#152 Jay on 06.23.12 at 7:59 pm

Glad it’s (mostly) working for you. I suspect that either your laptop’s BIOS or your battery’s BMS board need to re-calibrate itself. If you are lucky, going through a few full charge/discharge cycles will eventually do this. (If you are unlucky, they do not have a re-calibration scheme, and only go in one direction (down) and now can’t understand why your battery is lasting so much longer than it used to.) Try turning your laptop completely off, removing the battery, pressing the power button for a few seconds, and then putting the battery back in to see if that re-sets anything.

#153 Tom on 06.24.12 at 11:17 pm

I had no luck changing the cells in the Thinkpad T400 battery. Thus, I have 6 New LG Lithium 18650 Rechargeable Cells (3.7V 2600mAh), never used. Anyone in Chicago is willing to buy them. I received them in June.

#154 john on 06.27.12 at 12:13 pm

im trying to make a battery pack for my homemade speakers but i cant find a safety circuit that i could buy so i thought that i could use the circuit in the battery but i cant find the pins that are positive and negative and i still want to be able to charge the battery’s. The battery’s are from a old Sony vaio laptop.

#155 Jay on 06.27.12 at 1:10 pm

Hi John,

You might want to check out for a selection of battery management systems:
Pick the correct voltage for the number of cells you have. For a set of speakers, I don’t expect that the Amperage will be much higher than 500 mA or perhaps 1000 ma (same as 1 amp) if they are really big speakers. If your speakers have a power jack, they may also have a sticker that tells what their current draw is.

#156 john on 06.27.12 at 2:26 pm

the battery’s are SANYO li-ion 3.7v with a capacity of 1900 MAH. the thing is that i dont live in the us and i don’t want to order something outside my country and the speaker is just on medium sized speaker wit a small 5W apm that runs on 9-14vDC. so i need to know if i can use the circuit that comes with the battery pack or what would happen if i use the battery’s and charge them without the circuit.

#157 Jay on 06.27.12 at 3:18 pm

You could wire 3 cells in series (11.1 volts) to power your speakers. With only a 5 watt draw, they will never overheat your cells. The only danger is that if you leave them on they will completely drain the cells to 0 volts, which will kill them, but not in a spectacuarly burning way…just a slow death that won’t hurt anything but the cells. As long as you charge them before they get too low they will be fine.

The bigger danger is overcharging your cells. If you can find a regulated power supply that puts out exactly 11 or 11.1 volts and never goes higher, that would charge them safely (assuming that 3.7 volts is the correct charging voltage on a per-cell basis, some cells have lower charging voltages and some have higher ( up to 4.2 volts). As long as you are monitoring the voltage levels and remove the batteries when they are changed you can use just about anything to charge them, the harder bit is to find something that won’t overcharge them when left unattended.

#158 john on 06.27.12 at 7:13 pm

ok now you seam to know about this stuff so what kind of battery do you recommend i want the battery to be longlasting. do you recommend using the li-ion, a 12V 1,5-2AH lead acid battery or jsut some regular rechargeable AA battery’s.

thank you!

#159 Jay on 06.27.12 at 8:10 pm

1900 mAh li-ion batteries are basically 1.9 mAh batteries. Three (or four) of them would be close to equivalent to a “12 volt” battery (which typically ranges from 11-13 volts in actual usage, and higher when being charged. A 5 watt draw at 12 volts is 0.41 amps, which is 25% of the total 2 Ah capacity. The LiIon batteries would actually run this load for longer (closer to 4 hours) than the lead Acid battery (which has a 2 Ah Capacity, but only if discharged over 20 hours….not 4 hours…) They would also weigh less. The advantage of the 12 volt battery is that it won’t burst into flames (as easily) if you overcharge it, and you can find 12 volt lead acid battery chargers all over the place.

Regular rechargeable AA’s are typically NiMH chemistry, which is somewhere between Lead Acid and Li-Ion in capacity. AA battery chargers are also dead easy to find.

If you are looking for easy to purchase and charge, rechargeable AA batteries are hard to beat. Since you already have LiIon cells, they would make the best choice if you can find a way to charge them safely.

#160 john on 06.28.12 at 5:40 am

ok thank you for everything it was very helpfull!

but i want to know how you calculated how long the lifetime was so that i maybe could use it to get some batteries that would last even longer

#161 Jay on 06.28.12 at 6:54 am

The actual “lifetime” that a battery can drive a load depends upon the AH rating of the battery, and the rate at which you are discharging it, plus the battery chemistry, using something called the Peukert Number which is based upon the chemistry (and sometimes, brand) of the battery.

The easy way to get more life is to buy a battery with more AH rating. All things being equal, LiIon is better than NiMH, which is better than Lead Acid in most applications (except for ease of charging).

#162 Tom on 06.28.12 at 12:25 pm

If my laptop is plugged in 95% of the time. How do you setup the battery management to make the battery last the longest?

#163 Jay on 06.28.12 at 2:12 pm

Don’t start charging your battery until it is down to 70% capacity (30% discharged), and only charge it until it reaches 80% capacity. (Most laptops will fully charge the battery, assuming you want as much capacity as possible, so you may need to set things up to “not charge until 70%” and then manually unplug the battery once it reaches 80% to stop charging, then put it back in, or charge it to 100%, and then discharge it manually to 80%.

#164 shkence on 06.29.12 at 12:32 pm

Hi Jay,

I tried following your advice; by turning the laptop off, removing the battery and than restarting again and putting back the battery but no luck at this time.
I can’t understand, power meter shows o time left and my comp continue to work about one hour more, but the flash light continue to blink 4-5 times red and one time green. This does every time I insert the battery in my laptop. Strange ha?

many thanks again

#165 shkence on 06.29.12 at 12:35 pm

Is there any possible harm to my computer in relating to what mentioned above?
thanks again very much in advance

#166 Jay on 06.30.12 at 6:18 am

I ran into a problem like this with my laptop after refilling the battery. The BMS board didn’t “know” that the cells had been replaced, so assumed that they had the same (reduced) capacity of the old cells. This meant that the BMS board told the laptop’s power meter that the battery was essentially empty (zero on the power meter). BUT, since the cells could continue to provide power for a lot longer, the laptop would run for an extra hour or so…..

For me, my BMS was eventually smart enough to figure out that the cells had “recovered” and it re-set it’s “capacity available” numbers. It did take 5-10 charge cycles. If your BMS is not as smart, it may never reset it’s capacity available number.

#167 Jay on 06.30.12 at 6:20 am

If you run your laptop until the battery is actually empty, the laptop will shut down immediately due to loss of power. If your operating system is in the middle of writing something to disk when this happens, the file system may get corrupted. This could lead to having to run a chkdisk like program, or a completely corrupted hard drive (at very worst case scenario) that would require a re-format and re-install.

#168 shkence on 07.01.12 at 5:38 am

thanks Jay for you valued advises.
I will keep using same battery and see if anything changes.
I am wondering if I can replace NI -CD element with LI-Io cells that have PCB for a power tool. Is it safe. Can PCB of each cell protect the battery from overheating?

Do I have to remove PCB from each cell when I use them to replace to one old computer battery that has charging control circuit or should I use them with PCB. Does charging control circuit and PCB of each battery element conflict each other? Thx and Have a great day

#169 Jay on 07.01.12 at 8:10 pm

I’m not 100% sure that I understand your question. You should NEVER use a BMS PCB from a LiIon cell on a NiMH cell (or visa versa). However, if you have a LiIon pack of cells that is protected by a BMS system (and it provides the same voltage as a NiMH pack of cells) you should be able to replace the NiMH pack with the LiIon pack. If the pack is wildly undersized, it will overheat and the BMS system should shut it down, either by detecting the excessive current draw, or because the temperature sensor in the cells has triggered.

#170 shkence on 07.02.12 at 10:00 am

My apologize for a messy question.

1. can I replace Ni Cd batteries with Li-Io in batteries (with PCB) in a power tool. (of course the same voltage and higher mah)

2. If want to replace cells to laptop battery, and I am using li-io cells with PCB, do I have to remove the PCB from each cell before I use them and put them in laptop battery pack?
Thank you again very much,

#171 Jay on 07.02.12 at 11:03 am

1. Yes, you should be able to do this with no major problems. If the capacity of the battery pack is much greater, you may want to watch out for the motor on the tool overheating if you run it longer than it was designed for. Of course, you will have to use an appropriate LiIon charger, instead of the standard NiMH charger.

2. If you are replacing laptop LiIon cells, you should be able to re-use the existing circuit board. (So of the cells came with their own circuit board you can discard it). Some BMS systems will “die” and refuse to work if you disconnect them from power from a battery, so some people have “hot swapped” cells (soldering in the new cells before disconnecting the old cells). You must be careful that both the new and old cells have the same voltage so they don’t transfer too much current back and forth before the old cells are removed.

#172 ali hassan on 07.02.12 at 3:38 pm

i have laptop hp 6910p i want change the battry is 4400 mali ampaire i want make him 1200mah .each cell 3500mah and 6 cell make how to mah. battry voltage 10.6

#173 Jay on 07.02.12 at 9:59 pm

It sounds like your current battery has 6 2200 mAh cells in a 2 parallel 3 series arrangement. (2200 X 2 = 4400) (3 X 3.5volts = 10.6 volts)

If you replace your 2200 mAh cells with 3500 mAh cells, you will have a 3500 X 2 = 7000 mAh battery at 10.6 volts. The total capacity of your battery will be 2600 mAh larger.

#174 shkence on 07.06.12 at 4:42 pm

Thanks Jay,

Relating to question 2 that I mentioned earlier, I guess I can’t discard the existing circuit board of the battery but i have to remove the circuit board of each cell? Do I? Hope I got it right?

thanks a lot, it really helps

#175 Jay on 07.07.12 at 5:46 am

If each of your new/replacement cells has it’s own circuit board then it sounds like they have their own fuse/BMS built in that is different from a “whole battery” BMS that most laptop batteries have (which connects to each cell but has only a single circuit board). Your cells may be specialized or different chemistry from “standard” 18650 liIon cells, so I really can’t give you much advice.

In general, when you buy “raw” cells they won’t come with a BMS unless you pay extra for it.

#176 shkence on 07.11.12 at 2:59 pm

Yes Jay, new battery cells have their own fuse/BMS. So I am not sure do we have to remove the protection circuit before using them. China is producing a lot this types of batteries but I am not sure and haven’t tested these kind of batteries.
anyway thanks always for your valued explanations

#177 Jay on 07.11.12 at 8:00 pm

It sounds like they are just fuses that open under excessive heat. I don’t see any problems with leaving them in your circuit.

#178 shkence on 07.16.12 at 5:37 am

Hi again Jay,

I did some research on the internet where it is stated that: Li-Ion and Li-Poly battery packs should always be used with a protection circuit to prevent the cell from over charging or over dis-charging. Choosing the correct circuit and applying it appropriately is vital to the longevity your batteries and your own safety.

And this PCB is incorporated within the battery cell.
So I am not sure to remove it or not before using these cells in different battery packs that have their own charging/discharging control circuit.

here is the link:

thanks again and have e great day,

#179 shkence on 07.16.12 at 5:47 am

here is a link about batteries with PCB

#180 Jay on 07.16.12 at 1:38 pm

I see nothing wrong with leaving the protection PCB on the end of the cell, IF, and this is a BIG IF….you can still fit the cells inside the laptop battery compartment.

However, the protection will be redundant, as the purpose of the laptop battery circuit board is to control charging and discharging current to protect the cells. Redundant protection shouldn’t be a problem (unless the cell protection shuts things down before the laptop battery BMS board does, and tricks the laptop battery BMS into thinking the cell is completely dead when in fact it was just shut down by the protection circuit).

The big issue I see is that laptop batteries typically really jam the 18650 cells in, and I don’t think the cells with the protection circuits will fit well.

#181 TnF on 08.24.12 at 3:22 pm

Hello Jay. I have an Asus g73jh (laptop). After 2 years the battery one day died. Opened it, all cells having 0 voltage. They were some unprotected LG 18650, so i bought Panasonic NCR18650A to replace them (these are higher capacity and protected). I did the diy and connected the battery to the laptop. It shows that is charging but 0% charge. Voltage is reporting normally through HWINFO64 (14.48v).

I tried to charge with laptop closed, but nothing. It will not charge (though it’s showing it’s charging) and it will certainly not boot up from the battery alone. I checked the circuit board to find out if something is preventing it to work, and there is a Texas instruments IC (bq20z95):

Reading through technical documents, i found the pins that you connect to reset it, but with no success. Maybe i just need to connect exactly these pins together without touching any other pins, but it’s too small. Also i found out that the chip can use SHA-1 authorization, which will prevent me running any function if it is activated. Also there is a reset function(software) but i don’t know if it has to do anything with the hardware function:/ I’m thinking of trying to charge cells manually individually but i have no charger, plus now the tabs are welded together.

I’m stuck now, i don’t know what to do. These cells were not cheap either..Any help is appreciated. I can post pictures too.

Kind Regards,

#182 Jay on 08.25.12 at 8:28 am

Hi Ken,

It sounds like you have done much of what you can to try and re-set the BMS chip. I’m afraid I don’t have any specific advice to offer on that front.

How do you know it is not charging? Perhaps it is charging, but the BMS is not delivering power to the laptop? Typically when you purchase LiIon cells they come with at least a 1/2 charge from the factory. You can use a multimeter to check the voltage level of each cell (and all cells in series).

If you have a current regulated bench power supply, you can use it to charge single cells (or the entire series of cells) if set to the appropriate voltage and a low current (e.g. 0.1 amp).

#183 Keith on 10.22.12 at 3:38 pm

UltraFire BRC 18650 3000mAh 3.7V Li-Ion batteries – 887mAh! – YouTube

#184 Jay on 10.22.12 at 7:36 pm

Good to know! Thanks for doing the testing.

#185 Achintya on 11.03.12 at 1:14 pm

I have dell xps l502x laptop. The orginal battery died a few days ago. so instead of buying a compatible or genuine battery pack i decieded to rebuild it .I opened the battery case & found that there were 18650 lithium ion cells from sanyo 1000mah each . I serached on numerous websites and finally got panasonic 18650 3100mah battery. I installed them & then charged for nearly 2 hours (till the charging led switch off) but when i use it on battery it drains really fast just the same back up that i got with old cells…..any idea / suggestions please

#186 Jay on 11.03.12 at 6:44 pm

It may be that your BMS system hasn’t figured out that you have a new cells. So the percentage battery life goes down very quickly until it hits zero. BUT, after that, your battery actually still has 70-90% of it’s charge, and the laptop will continue to work for hours while the BMS keeps reporting 0% charge left. (this happened on my laptop).

If you keep running the laptop down until the battery actually dies and then recharge it and do it a few more times the BMS should hopefully “re-calibrate” itself.

#187 Achintya on 11.07.12 at 6:58 am

Jay thanks a ton for answering my query. One more thing i want to ask is that as i installed cells with (3100mah) more than double the capacity installed before (1000mah) will the BMS system able to charge these cells upto 3100mah or it will cut down charging after say 1000mah charging for each cell is done…?

#188 Jay on 11.07.12 at 8:57 am

Each BMS system is different, but in general they will use voltage to recognize when the cells are “full” so larger capacity cells will be charged until they are full. (It could take longer to charge them than the original cells, as the BMS may limit the total input current based upon it’s assumption that you have smaller cells in the battery still.)

#189 Danny on 12.09.12 at 6:11 am

Hello Jay, great work you have done with your battery pack.

I have a dead IBM T43p 9cell battery with 7200mAh capacity. I recently cracked open it and decided to follow your procedure. I will definitly dodge the Ultrafire cr@p and buy decent ones. My question is the following: Obviously I should be looking for 2400mAh batteries and buy 9 of them. I know I can buy 2600mAh batteries and have them installed, but what the highest mAh rating can I buy and install? Can the battery electronic board hold for example 5000mAh batteries?


#190 Jay on 12.09.12 at 7:04 am

Your batteries circuit board should have no problem with you increasing the capacity of the cells (the voltage says the same). It will of course take longer to charge the cells (and longer to discharge, which is the point). Your main limitation will be how much capacity you can fit in the space, as you are limited to cells of the same physical dimensions as your original cells. I doubt you can find 18650 cells that actually have 5000mAh capacity, regardless of what their packaging says.

#191 Danny on 12.09.12 at 8:30 am

Hello Jay, thank you for your reply.

Yes my bad, I was just googling the reviews on the 18650 batteries and I understand now that the TRUE highest available is 3100mAh.

Need to show you a picture of my battery core and ask you about something related to it. Tried to email you but didn’t get through. How can I do that?


#192 Jay on 12.09.12 at 8:20 pm

You should be able to send an email to me at the email address on my main contact page (firstname at, make sure you spell my last name correctly (without an “i”). If you are unable to attach the image, you can use a free image hosting service such as and send the url instead. (Or, you could do that and just submit your question as a comment here…)

#193 igor on 12.15.12 at 3:23 am

Not worth the bother.

#194 Jay on 12.15.12 at 4:38 am

After having done it, yes, I agree ;> The only situation where the labor is worth it is if you simply can not find replacement batteries for sale on the market, or you can’t find replacement batteries using the largest capacity 18650 cells and you absolutely need/want the best cells in your battery.

#195 Bill on 12.27.12 at 11:57 am

Has anyone heard of someone who will take your old laptop battery pack and do this for you? There must be someone.. Seems that would be an excellent business opportunity, I have tried the aftermarket crap and its pretty poor, using the manufacturers controller appears to be the hot setup.

#196 Pera on 01.31.13 at 2:04 am

This site is very inspirational, but something is really boring me.
OK I understand some battery pack when you unsolder the cells from the battery pack it is not guarantied to the chip to kill him self or not.
But I ask myself is it the same thing when:
1. the cells was dead and have a nice 0V voltage, and
2. I unsolder the cells from the battery pack?
I understood one thing, the chip to be working must have some voltage and some current, when all batteries are dead, there is no voltage and no current and for the chip is absolutely the same thing you do the one way or a hard way.
Another thing, If you want to parallel two batteries one dead and one good replacement, it is not always possible to get up voltage to the dead batteries close enough to the new one. In my experience which is not absolutely big, I tried something with dead and not dead old batteries 18650.
I tried to charge them and to shock them like they suggest with NiMH when they are dead. The voltage was 5V, 12V, and 18V with some resistors of 2,7 Ohms and 5.6 Ohms 7W. The measured currents for the two batteries in parallel (both dead) was something like 400mA, 1.2A and 2.4A. Because I don’t know for sure what is the allowed current to charge and beside thing i was wanted to shock them I started with higher voltage and current from 4.2 suggested. And for the big current I was charged for a 5-10 seconds.
And I was afraid of boom explosion, but nothing happens not just worm up nothing cold like I didn’t charge at all. But The voltage was enough and after one week the old good batteries was OK good and the dead was but but better one good, but not enough to be like old one good 1.5V or 180mV, yes they was bad OK.
The opening battery pack: believe me it is not for everybody the hand is on a thin ice to be sliced from the screw driver or pierced and must have a strong hand both to control battery pack not to slip out from the hand. It is not for everybody.
Another battery pack I opened up the new one laptop (sorry for a both I don’t wrote the laptop model number) all batteries have a voltage 10mV or a zero.
And you suggest me to charge them up to voltage close enough to the 3.7V. OK But How? I think If original charger board failed to charge them up How can I will succeed ? OK I was unsolder them battery cells, guided with my logic that the chip is already dead not because i unsolder the cells but because of low voltage of the cells. OK I tried the same thing with the first one old batteries to charge them up. But This time success was failed completely. The current was almost 0mA whatever voltage I started and it was the end of the test. Please I want from you to confirm or to explain me am I in right with logic’s outlined hear or not.
Because I have my opinion. Thanks in advance.

#197 Jay on 01.31.13 at 8:38 am

If your existing batteries are already at 0 volts, the BMS system is probably shut off already. In that case, I don’t see any benefit in trying to bring them up to the voltage of your replacement batteries and soldering them in parallel. You can probably just cut them out and then solder in the new cells.

#198 shree on 02.12.13 at 9:49 pm


My laptop battery meter shows the following. Design Capacity – 48840, Last Full Charge – 5740 and wear level at 85%. It is not charging to the full extent. So I am trying to replace my sanyo as09c31 battery with new cells. I opened up the casing and checked the current voltage in the cells and its shows 10.8 V. Is it a battery issue or something else is not correct ?

#199 Jay on 02.13.13 at 8:35 am

10.8 volts sounds like a 3 cell battery (or 6 cells, 3 sets of 2 parallel cells, or 9 cells, 3 sets of 3 parallel cells) That voltage is normal for a set of 3 LiIon cells in series. It sounds like your cells are just old, but still provide full voltage, even if their capacity is only 15% of new. You can probably swap them out for new cells and get a lot of your capacity back, although you may need to jumper in the new cells before you remove the old cells to keep the charge controller chip from realizing that you removed the old cells. (Some chips disable themselves when/if they detect zero voltage.)

#200 shree on 02.13.13 at 10:50 am

It is 3 sets of 2 parallel cells. Pls explain what is jumper ? Is it like replace cells without disconnecting the circuit.

#201 Jay on 02.13.13 at 2:06 pm

Set up your new cells in a 3 set of 2 parallel cells as well. Make sure the new cells are also at 10.8 volts (same as the old cells) so that not much current will flow when you connect them. Then, connect the new cells in parallel with the old cells, including any connections between the 3 sets of cells. (The BMS uses connections into the middle of the pack to monitor voltage and charge levels for each set of 2 parallel cells individually.)

Once you have the new cells electrically connected, you can disconnect the old cells, and the BMS module will never know that you replaced the cells….except that the battery cells will miraculously start holding more and more capacity than they used to ;>

#202 pradeep on 02.17.13 at 5:52 am

Jay, HP technical support told me that if I replace my orignial 4 Ah battery by even say +/-.5 i.e. 3.5 or 4.5 Ah then it may possibly crash laptop. I guess its not correct and I should be able to replace with 8800mAh battery -or do you I should better prefer buying 4.4 Ah, since original 4 Ah battery is not available and I may not feel easy replacing cells, specially soldering etc. Another question, does compatible batteries are safe to buy ?

#203 Jay on 02.17.13 at 6:46 am

HP Engineers would be able to tell you for sure, as I don’t know much/anything about the specific HP laptop you have. However, I doubt that your tech support contact knew what they were talking about. Unless the software/firmware on the laptop was badly miswritten, it will work with a higher capacity battery. It is possible that a particular BMS chip in a specific battery is programmed to expect cells of a certain AH capacity, but at least with the battery that I used (which was a generic battery, not an OEM battery) the BMS adjusted to the higher capacity cells.

Buying a replacement battery will always be easier and more cost effective (if you consider your time worth money) than replacing cells. Many replacement/generic batteries are as good as the OEM equiptment, but some brands are made with sub-standard cells and are not as good. Read reviews, try to avoid deals that look too good to be true, etc…

Perhaps you want to buy a generic laptop battery and use that for another year or two, and if you need another one, replace the cells in it with higher capacity cells. In my experiance, the OEM batteries have more restrictive programming on their BMS chips, which in some cases mean that if you remove the original cells the BMS refuses to charge new cells. (If it detects that a cell has “died” by going to zero voltage, it refuses to charge again.)

#204 SUDDU on 02.27.13 at 8:01 am

Hello Jay, am using Lenovo 3000 Y500 as my laptop battery dead in stage. It contained 10.8 volts, 4.8AH (6 cells, 3 sets of 2 parallel cells). As I saw the reviews on internet regarding refilling of Laptop battery, I had been working on it. I had opened the battery pack safely, and replac the old one with new one as they are before. After that I connected to my laptop. It is showing ” 0% available (plugged in,not charging)”.
Can you help me regarding this problem….
Thank you…

#205 Jay on 02.27.13 at 1:48 pm

I’m afraid I don’t have any specific solution to your problem. I recommend that you shut down your laptop completely, remove the battery, and re-insert it, and then leave it plugged in overnight. That may re-set the BMS chip. Alternatively, it may be that the BMS chip will never allow you to charge the battery as it detected that the cells “died” and doesn’t realize that they were replaced.

#206 Xavier on 03.28.13 at 5:13 pm

I’m experiencing the same than #137 with my 3×2 CGR18650CG cells powering a HannsNote 10″, when the + current is not passing thorugh the PCB. I discharged the bateries by using a lamp and charged them later with the notebook, without problems (well it took something like 9hrs for a full charge). Anyway the full charged set was not feeding/recogniced by the notebook. Any improvements within this time?

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